The invention relates to a reflector lamp comprising a light source energizeable for emitting light, a reflector body having a reflective surface for directing light emitted by the light source, and a lamp base having lamp contacts electrically connected to the light source.
Such lamps are well known in the industry and include, for example, parabolic aluminized reflector (PAR) lamps. PAR lamps have a sturdy lamp envelope with a pressed glass reflector body having an internal parabolic reflective surface and a pressed glass cover hermetically sealed to the reflector body. Historically, the light source has been an incandescent filament. More recently, the light source has been a halogen burner, which provides greater efficacy than with a conventional bare incandescent filament. Still further improvements in the art have led to the use of halogen burners which include infrared reflective coatings on the burner capsule or on a sleeve within or outside the burner capsule. The coating reflects otherwise-wasted infrared radiation back onto the filament. This raises the temperature of the filament and increases useful light output for a given power consumption.
PAR lamps come in many different sizes and have many different applications. These include general indoor and outdoor spot and flood lighting, such as for buildings, statues, fountains and sports grounds, as well as accent lighting, such as for retail store window displays, hotels, restaurants and theaters.
As part of a worldwide movement towards more energy efficient lighting, recent government legislation in the United States (commonly referred to as the National Energy Policy Act "EPACT") has mandated lamp efficacy values for many types of commonly used lamps including parabolic aluminized reflector (PAR) lamps. These minimum efficacy values became effective in 1995 and only products meeting these efficacy levels are allowed to be sold in the United States. The efficacy values for PAR-38 incandescent lamps have been established for various wattage ranges. For example, lamps of 51-66 W must achieve 11 lumens per Watt (LPW), lamps of 67-85 W must achieve 12.5 LPW, lamps of 86-115 W must achieve 14 LPW and lamps in the range 116-155 W must achieve 14.5 LPW.
There are few PAR 38 lamps currently on the market with a reflective coating of aluminum and an incandescent filament which pass the EPACT standards and which have a commercially acceptable life of 1000 hours. Those that do barely exceed the minimum standards, and further substantial improvements seem unlikely. Accordingly, the market is rapidly shifting to
lamps which have halogen burners or halogen IR burners.
However, one disadvantage of commercial halogen and halogen IR lamps is their relatively short lifetime for acceptable efficacy. For example, a commercially available 90 W lamp has an average lifetime of about 2500 hours while that of a 60 W halogen IR lamp is only slightly greater at 3000 hours. It would be desirable to have a significantly longer lifetime since re-lamping, especially for fixtures in high places, can easily exceed the cost of the lamp being replaced. Another disadvantage is the luminous efficacy is limited to below about 20 LPW. For example, the 90 W halogen PAR lamp has a luminous efficacy of about 16 LPW while the 60 W
with a halogen IR burner has a luminous efficacy of about 19 LPW. Further improvements in efficacy for these lamps at a fixed life would be expected to be less than about 5%. Still another disadvantage is that the color temperature is limited for tungsten filament lamps to a maximum of 3650 K, the melting point of tungsten. Typically, however, the color temperature is confined to a range of about 2600-3000 K to achieve a commercially acceptable lamp life. It would be desirable to offer lamps with a different color temperature because this enables the lamp to be tailored for specific applications. For example, it is generally desirable that for cool environments a warm color temperature (for example 3000 K) is desired whereas for a warm environment a cool color temperature (for example 4500 K) is desired.
Still other reflector lamps are known which include a blown glass envelope and contain a bare incandescent filament. These are generally known as "R" lamps, and have even lower luminous efficous than the PAR lamps, for example on the order of 9-11 LPW, and the same colorimetric limitations.